At noon the water level in a storage tank was 125 cm. After pumping out some water, the level fell to 90 cm.
a. (i) Represent the situation above by a linear equation in one variable taking x as the number of centimetres of water pumped out.
b. (ii) Solve the equation to find the value of x.
c. (iii) Check your result by substitution in the original equation.